Many medical procedures require repeated and prolonged access to a patient's vascular system. For example, during treatment of diabetic patients, blood is removed for filtering and purification externally to the body, to make up for the inability of the patient's kidneys to carry out that function naturally. In other procedures, access to the patient's vascular system is necessary to administer antibiotics, drugs, nutrition or chemotherapy agents on a long term basis. Typically access is obtained through a vein or artery, using a catheter secured to the patient and a needle of the catheter penetrating the blood vessel.
Some of these procedures are repeated several times a week and it is impractical and dangerous to insert and remove the catheter for each procedure. The catheter thus is implanted semi permanently with a distal end remaining within the patient, in contact with the vascular system, and a proximal end remaining external to the patient's body. The proximal end is sealed after the medical session is completed, to prevent blood loss and infections. The distal end of the catheter thus remains in the patient's body, often for extended periods of time. In some cases, the catheter may be sutured in place and remain within the patient for several years.
A clinical drawback to leaving these devices in the patient for extended periods is that bacteria tends to attach to the surfaces of the catheter, multiply, and produce a biofilm layer that can result in sepsis. These infections may lead to severe complications that often are debilitating and may be life-threatening. Anti-infective agents including, for example, antibiotic and other antimicrobial coatings, have been used on the catheters to combat these infections. For example, chlorhexidine-silver sulfadiazine and rifampin-myinocycline coatings, among others, have been applied to the polymeric surfaces of catheters. This solution however has not proved satisfactory, as the agents in the coatings are often released in a short time interval after implantation of the device, soon leaving the catheter open to infection.